Synthesis Of Microcapsule Containing Compound Paraffin And The Modification Of Insulation Material With Rice Husk Ash

With the global energy crisis intensified,the development of new energy and the saving of existing energy have been today’s hot topics.It is one of the important ways to achieve the social energy conservation by developing the building heat preservation material actively to save the energy consumption of buildings.Phase change insulation material is a kind of new building energy-saving material,which can store the energy when it’s phase changes.Paraffin is the common used organic phase change materials,it has many advantages, such as larger phase change latent heat, no supercooling and the phase changes at daytime temperature.In order to prevent the leak of melted paraffin and achieve energy storing,it is aways wrapped as microcapsules before used with the other building insulation materials.Rice husk ash (RHA) is a kind of solid waste produced by burning the rice husk.By the nature of light,porous and with abundant amorphous SiO2inside, rice husk ash is a good insulation material which has excellent thermal insulation properties and pozzolanic activity. So the thermal insulation properties of phase change insulation material could be improved by adding the rice husk ash to it.This paper mainly includes four parts of contents.The first part was the compounding of solid paraffin and liquid paraffin.The melting point of solid paraffin was lowered by mixing it with liquid paraffin.The phase change point was determined by the means of curve law of step and the DTA analysis was used to detect the thermal property of complex paraffin in the melting process.The experiment results show that, with the increase of the liquid paraffin,the melting point of compound paraffin is gradually lowered, the cooling curve is getting smoother,the melting range trends to be longer, the thermostability and the enthalpy of phase change is decreased and changed most significantly when the liquid paraffin is between50%-67%.The second part is the synthesis and characterization of microcapsules containing compound paraffin.The phase change microcapsules for thermal energy storage containing compound paraffin with urea formaldehyde resin was synthesized by means of in-situ polymerization based on the fundamental formula.The core rate and the encapsulation efficiency of microcapsules was calculated.The performance of the microcapsules was detected by the scanning electron micrograph(SEM), granulometry and differential scanning calorimetry(DSC).The experiment results show that,The core rate of the microcapsules is26.32%,the encapsulation efficiency is15.68%,the phase transition temperature is about50℃,the microparticle size is distributed wide and the mean grain size is257.3nm, there are also some irregular knots on the surface of the microcapsules.The third part is the optimum choice of the technical parameters. The influences of means of emulsification, core-wall ratio, emulsifier and promoter(NaCl) content on the performance of microcapsules were investigated through the single-factor experiments.The experiment results show that,the optimum process parameters are the OP emulsifying agent6%,the core-wall ratio1.30and the promoters(NaCl)18%～36%,the core rate of the microcapsules optimized is higher than78%, the encapsulation efficiency is more than43%and the enthalpy of phase change is high to112kJ/kg,the microcapsules is shaped well and has a smooth surface.The fourth part is the preparation of the phase change insulation material modified with RHA. The performance such as the thermal conductivity,the compressive strength,the density and the water absorption of the phase change insulation material was determined. The performance changes with the increasing amount of RHA have been studied.The experiment results show that,when the dosage of RHA is8g(4.6%of solid binders), the density of the insulation material has decreased19.59kg/m3(8.1%decreased),the thermal conductivity has decreased0.028w/(m·k)(33%decreased) and the compressive strength has increased0.04MPa(6.7%enhanced), the water absorption rate rise from15.4%to16.8%. So the RHA have similar heat preservation effect with the expanded perlite while the water absorption rate is much lower than it.